Image data coding and/or decoding system capable of high-efficient coding

ABSTRACT

An image data coding system comprises a screen-area determining means for determining the area of a screen reproduced on the basis of an input image data; a code-amount assigning control means for controlling regions to which data on the screen are to be assigned and the code amount assigned to each of the regions, on the basis of the results determined on the area of the reproduced screen; and a coding means for coding the image data signal inputted in accordance with the code amount assigned to each of the regions.  
     In an image data coding and/or decoding system, a coding system performs the two-dimensional orthogonal transform of picture signals of all the pixels with respect to inside blocks and of only picture signals of pixels contained in a content with respect to edge blocks, in accordance with a map signal indicative of the position and shape of the content, and it codes the map signal. A decoding system selects an orthogonal transform coefficient necessary to reproduce an image of a desired resolution, from coded orthogonal coefficients on the basis of a coded and resolution-transformed map signal, and it performs the two-dimensional inverse orthogonal transform of all the coefficients with respect to the inside blocks and of only the coefficients contained in the content with respect to the edge blocks, to derive a resolution-transformed regenerative signal.

BACKGROUND OF THE INVENTION

[0001] The present invention relates generally to an image data codingand/or decoding system which can carry out high-efficient coding ofpicture signals to transmit and store. More specifically, the inventionrelates to an image data coding system which can code and transmitpicture signals to display an image on a liquid crystal display with asmall screen which can be built in a wristwatch and so forth.

[0002] In the coding of image data used for a visual telephone (TVphone), a television conference and so forth, the image data efficientlycompressed utilizing human's visual characteristic are used. The human'svisual characteristic with respect to the distortion of a pictureutilized here are as follows (see “Image Information Compression”,issued by Japanese Television Society and complied under the supervisionof Hiroshi Harashima, page 12).

[0003] (1) Frequency Characteristic in Distortion Perception

[0004] Distortion varying with elapsed time and distortion with highspatial frequency are difficult to be visible to the naked eye.

[0005] (2) Relationship with Pattern of Image

[0006] Distortion is easy to be perceived at the flat portion of theimage, and difficult to be visible on the contour portion of the image.However, this is the case of a still picture. In a moving picture, thedistortion on the contour portion serves as an edge busyness toconversely offend the eye.

[0007] (3) Relationship between Image and Motion

[0008] When a picture is moving at a higher speed than a given speed andthe user's eyes can not follow its motion, the perception sensitivity todistortion lowers.

[0009] (4) Relationship with Switching of Scene

[0010] Immediately after a scene has been switched, the distortion isnot to be visible to the naked eye if the resolution considerablylowers.

[0011] (5) Relationship with Brightness of Screen

[0012] The more the screen is dark, the more the picture distortion ofthe same level is easy to be visible to the naked eye.

[0013] (6) Color Signal and Luminance Signal

[0014] Since distortion by color signals is more difficult to be visibleto the naked eye than that by luminance signals, for example, it ispossible to thin out sampled points of the color signals.

[0015] In addition, since visual acuity (spatial resolving power) on theperipheral portions of the visual field is worse than that on thecentral portion thereof under the influence of the distribution ofvisual receptor cells on retinas, it is necessary for an user to movehis eyes (eye movement) in order to obtain information such as shape,structure and detail contents (see “Image Information Compression”issued by Television Society, published by Ohm, page 41). Therefore, todetermine the definition of the picture in view of human's visualcharacteristic is dominated by the movement of human's eye serving as asubjective factor in addition to the resolution of the picture servingas an objective factor.

[0016] On the other hand, when a human looks at an object, if the objectis small, it is possible to recognize the whole shape and so forth ofthe object by staring a specific range around a point. However, if theobject is large, it is necessary to closely observe a wide rangeincluding a large number of points to recognize the whole shape and soforth of the object. When he watches a television receiver, if itsscreen is large, a large number of closely observed points aredistributed in a given range by frequently moving his eyes, but if thescreen is small, the range wherein the closely observed points aredistributed does not so extend.

[0017] It is disclosed in “Estimation Technique of Image Quality andTone Quality” (edited Television Society and published by Shokodo, page118) that since the display screen in a high quality television systemwhich rapidly approaches to implementation in recent years is greaterthan those of current television systems, the closely observed pointsdistributing ranges in these systems are different. FIG. 5.22 on thesame page of this paper shows the measured result of proportion of theclosely observed points distributing range to the area of the screenwhen observing a high quality television system and a current televisionsystem on a standard observation condition using a program of the samecontent. This figure is expressed by approximating to an ellipse withthree times as large as the standard deviation assuming that the closelyobserved points lie on a normal distribution in horizontal and verticaldirections when the center of the screen is the origin. It is also shownthe experimental results that the proportion of the distributing rangeof the closely observed points to the area of the screen is about 60% inthe current television systems, but it reaches about 80% in the highquality television system. That is, as the size of the screen decreases,the proportion of the distributing range of the closely observed pointsdecreases and the range concentrates on the center of the screen.Therefore, since the spatial resolving power of the visual sensation onthe peripheral portion of the screen is inferior, the informationcompression can be efficiently carried out by lowering the spatialresolution or by weighting the assignment of the distortion inpreprocessing.

[0018] By the way, as a method for efficiently compressing the measureof information using the difference between the visual characteristic atthe central portion of the visual field central vision) and the visualcharacteristic at the peripheral portion of the visual field (peripheralvision), there is a method disclosed in, for example, “Visual PatternImage Sequence Coding” (August, 1993, IEEE TRANSACTIONS ON CIRCUITS ANDSYSTEMS FOR VIDEO TECHNOLOGY, VOL.3, NO.4, pp-291-301). In the techniquedisclosed in this literature, a function relating to the position ofradius r from the central point of the screen is derived, and theresolution on the peripheral portion of the screen is lowered using thisfunction.

[0019] In addition, as a method for performing the informationcompression by changing the distribution of the assigned code amount ina visually important region and an unimportant region, there are twomethods as follows.

[0020] One of the methods has been proposed as applied to a videotelephone (Japanese Patent Application Laid-open No. 1-80185 (1989)“Moving Picture Coding Method”). In this method, on the assumption thatthe closely observed points are concentrated on the face of the oppositeparty for the telephone conversation, the face region is detected toassign many code amount on the detected face region.

[0021] Another method is also applied to a video telephone similar tothe aforementioned proposal (Japanese Patent Application Laid-open No.5-95541 (1993)). Similar to the aforementioned proposal, by detectingthe face region to apply a spatial-temporal filtering to a region otherthan the face, the code amount produced in this region other than theface is decreased, and the code amount assigned in the face region isincreased.

[0022] Both of these conventional methods pay attention to human'svisual characteristic, and provide a natural picture to a person whichvisually recognizes a reproduced picture, by changing the coded dataamount so that the coding data amount in the region in which the closelyobserved points are concentrated in the distribution of closely observedpoints, is different from the coding data amount in the region in whichthe closely observed points are not so concentrated.

[0023] As mentioned above, in both of the conventional image data codingmethods, the information compression has been efficiently performedusing human's visual characteristic by restraining the code amountproduced in a visually unimportant region and by increasing the codeamount assigned to a visually important region. However, both of thetechniques disclosed in the aforementioned two publications onlyclassify the regions in the screen on the basis of the degree ofconcentration of the distribution of closely observed points, to varythe code amount assigned to each of the regions, and these techniques donot consider human's visual characteristic that the distribution ofclosely observed points is different by the size (area) of the screen asdescribed in the aforementioned literature “Estimation Technique ofImage Quality and Tone Quality”.

[0024] In addition, there are problems in that when the image data aretransmitted via a radio transmitting channel having a narrower bandwidththan that of a wire transmitting channel, the resolution of thereproduced picture is generally decreased by the limit of thetransmitted amount due to the narrow bandwidth, so that the size (area)of the screen is necessarily decreased.

[0025] By the way, in conventional image data coding systems, forexample, in moving picture data coding systems defined by MPEG, afterinputted picture signals are divided into square blocks of 8×8 pixels asshown in FIG. 55, the two-dimensional discrete cosine transform (DCT) isperformed for coding.

[0026] On the other hand, in “Applying Mid-level Vision Techniques forVideo Data Compression and Manipulation” (M.I.T. Media Lab. Tech. ReportNo.263, February 1994), which will be hereinafter referred to as“Literature 1”, J. Y. Wang et. al. disclose that picture signals aredivided into a background and a subject (which will be hereinafterreferred to as a “content”) for coding, as shown in FIG. 56. Thus, inorder to code the background and the content separately, a map signalcalled a alpha map indicative of the shape of the content and itsposition in a screen is prepared. In this coding method, it is possibleto vary the picture quality content by content and to reproduce only aspecific content. However, as shown in FIG. 55, in a case where theinterior of a screen is divided into square blocks for coding, it isrequired to separately process the blocks containing the boundaryportion of the content, i.e. the edge blocks between the inside andoutside of the content, as shown in FIG. 57.

[0027] It has been also proposed a method for coding picture signalsafter dividing the interior of a screen into blocks of optional shapesso as to adapt to statistical characteristic in the screen and to theshape of a content. Such a method for performing the orthogonaltransform of an optional shape is disclosed in “Examination of VariableBlock Size Transform Coding of Image Using DCT” (Matsuda et. al.,Singaku-Shuki-Daizen D-146, 1992), which will be hereinafter referred toas “Literature 2”. In this specification, this transform method will behereinafter referred to as “AS-DCT”. In AS-DCT, first, one-dimensionalDCT is performed in a horizontal (or vertical) direction as shown inFIG. 58(a), and then, after it is rearranged in order of the low of theDCT coefficient as shown in FIG. 58(b), the one-dimensional DCT isperformed in a vertical (or horizontal) direction.

[0028] Also, in “Estimation of Performance of Variable Block ShapeTransform Coding of Image Using DCT” (Matsuda et. al., PCSJ92, 7-10,1992), which will be hereinafter referred to as “Literature 3”, thecoding efficiency has been improved by selecting the order of highercoding efficiency as a result of practical coding, as the order of thetransform in the horizontal and vertical directions.

[0029] Further, “Image Data-Coding Techniques—DCT and Its InternationalStandard—” written by X. R. Rao and P. Yip and translated by HiroshiYasuda and Hiroshi Fujiwara (7.3, pp164-165, Ohm), which will behereinafter referred to as “Literature 4”, discloses a method forperforming the resolution transform of picture signals using thetwo-dimensional DCT. That is, it is possible to transform the resolutionby taking out a part of the DCT coefficient derived by thetwo-dimensional DCT to inversely transform by the DCT of a differentdegree, as shown in FIG. 59.

[0030] In a picture system such as a graphic display, in order toactualize various image effects, it is desired to perform the resolutiontransform of a content in a screen for the reduction and enlargementthereof. Since there are contents of various shapes, it is required toperform the resolution transform of contents of optional shapes.However, for example, in the AS-DCT which is a method for performing theorthogonal transform of optional shapes disclosed in the aforementionedLiterature 2, it is impossible to actualize the resolution transform ina case where a block to be transformed is an edge block, i.e. a blockcontaining the boundary portion of a content.

[0031] In addition, there are problems in that the coding efficiency toan edge block is low in the AS-DCT and other methods for performing theorthogonal transform of optional shapes.

SUMMARY OF THE INVENTION

[0032] It is therefore an object of the present invention to eliminatethe aforementioned problems, and to provide an image data coding systemwhich can efficiently compress information by changing only theassignment of the code amount without changing the absolute amountthereof in accordance with the decreasing of the size of a reproducedpicture display, in view of the relationship between the size (area) ofthe screen and the distributing area of closely observed points.

[0033] In order to accomplish the aforementioned and other objects, animage data coding system, according to the present invention, comprisesa screen area determining means for determining the size (area) of ascreen reproduced on the basis of inputted image data signals, a codeamount assigning control means for controlling the assignment of thecode amount of data for every region on the screen on the basis of theresults of determination, and a coding means for coding the image datasignals inputted in accordance with the code amount assigned to everyregion.

[0034] With this construction, the weight function for assigning thecode amount corresponding to the size of the screen is set 80 as to bechanged by internally analyzing the inputted image data signals todetermine the size of the screen, or by designating the size of thescreen in an externally manual set mode. The assigned amount of the codeamount is determined using the set weight function, and the coding ofthe image data signal is performed on the basis of the assigned amount.Therefore, the assignment of the code amount is changed using the weightfunction in accordance with the area of the screen, so that it ispossible to provide the optimum screen for practical use by onlydetermining or designating the size of the screen if the weight functionis set in view of human's visual characteristic.

[0035] In an image data coding system, according to the presentinvention, the screen-area determining means may internally determinethe area of the screen of the produced picture on the basis of theamount of the inputted image data signals and so forth, or externallydesignating the size of the screen in a manual operation. In the case ofthe determination by internal processing, the amount of the image datasignals may be detected to detect the resolution of the produced screenon the basis of the number of pixels of the produced screen.Alternatively, the information relating to the size of the screen, whichinformation are included in a part of the image data signals, may betransmitted to analyze the information by a determining means todetermine the size of the screen.

[0036] In addition, it is an object of the present invention to providean image data coding and/or decoding system which can perform theresolution transform of the blocks containing the boundary portion of acontent.

[0037] It is also an object of the present invention to provide an imagedata coding and/or decoding system capable of high-efficient coding ofthe blocks containing the boundary portion of a content.

[0038] According to the present invention, the aforementioned and otherobjects can be accomplished by image data coding and/or decoding systemsas described below.

[0039] According to a first aspect of the present invention, an imagedata coding system comprises:

[0040] a first coding means for coding a map signal indicative of theposition and shape of a content in a screen inputted for every squareblock of picture signals to be coded;

[0041] an orthogonal transform means for performing the orthogonaltransform of the picture signals in accordance with the map signal tooutput an orthogonal transform coefficient; and

[0042] a second coding means for coding the orthogonal transformcoefficient derived by the orthogonal transform means,

[0043] wherein the orthogonal transform means performs thetwo-dimensional orthogonal transform of the picture signals of all thepixels with respect to the blocks located inside of the content, andperforms the two-dimensional or one-dimensional orthogonal transform ofonly the picture signals of the pixels contained in the content withrespect to the blocks containing the boundary portion of the content.

[0044] For example, with respect to the pixels in the blocks containingthe boundary portion of the content, the orthogonal transform means mayperform the one-dimensional orthogonal transform in the horizontal orvertical direction after rearranging the pixels contained in the contentin the horizontal or vertical direction, and performs theone-dimensional orthogonal transform in the vertical or horizontaldirection after putting the derived transform coefficients in order ofthe lower band of coefficient,

[0045] In this case, it may be provided with a correlation detectingmeans for detecting the respective correlations in the horizontal andvertical directions of the picture signals inside of the content, toswitch the direction of the one-dimensional orthogonal transform S0 asto perform the one-dimensional orthogonal transform in order of thedirection that the correlation is higher.

[0046] An image data decoding system adapted to the image data codingsystem, according to the first aspect of the present invention,comprises:

[0047] a first decoding means for decoding a coded map signal indicativeof the position and shape of a content in a screen inputted for everysquare block of picture signals;

[0048] a resolution transform means for performing the resolutiontransform of the map signal decoded by the first decoding means;

[0049] a second decoding means for decoding coded orthogonal transformcoefficients;

[0050] a coefficient selecting means for selecting an orthogonaltransform coefficient necessary to reproduce an image of a predeterminedresolution, from the orthogonal transform coefficients decoded by thesecond decoding means, on the basis of the map signalresolution-transformed by the resolution transform means;

[0051] an inverse orthogonal transform means for performing the inverseorthogonal transform of the orthogonal transform coefficient selected bythe coefficient selecting means; and

[0052] a reproducing means for deriving a regenerative picture signalresolution-transformed from the results of the inverse orthogonaltransform by the inverse orthogonal transform means,

[0053] wherein the inverse orthogonal transform means performs thetwo-dimensional orthogonal transform of all the coefficients withrespect to the blocks located inside of the content among the orthogonaltransform coefficients selected by the coefficient selecting means, andperforms the two-dimensional or one-dimensional inverse orthogonaltransform of only the coefficients contained in the content with respectto the blocks containing the boundary portion of the content.

[0054] For example, with respect to the blocks containing the boundaryportion of the content, the inverse orthogonal transform means mayperform the one-dimensional inverse orthogonal transform in thehorizontal or vertical direction after rearranging the transformcoefficients contained in the content in the horizontal or verticaldirection, and performs the one-dimensional inverse orthogonal transformin the vertical or horizontal direction after rearranging them to theformer positions of pixels.

[0055] When the first image data coding system switches the direction ofthe one-dimensional orthogonal transform so as to perform theone-dimensional orthogonal transform in order of the directiondetermined that the correlation is higher in the horizontal and verticaldirections of the picture signals inside of the content, the first imagedata decoding system may switch the direction of the one-dimensionalinverse orthogonal transform on the basis of the switching informationof the first image data coding system.

[0056] According to a second aspect of the present invention, an imagedata coding system comprises:

[0057] a first coding means for coding a map signal indicative of theposition and shape of a content in a screen inputted for every squareblock of picture signals to be coded;

[0058] an average value separating means for outputting an average valueof the values of pixels inside of the content, with respect to blockscontaining the boundary portion of the content in the picture signals,in accordance with the map signal, and for separating the average valuefrom the values of the pixels inside of the content and for setting thevalues of pixels outside of the content to be zero for output thereof;

[0059] an orthogonal transform means for performing the two-dimensionalorthogonal transform of the signals from which the average value hasbeen separated by the average value separating means, to outputorthogonal transform coefficients; and

[0060] a second coding means for coding the orthogonal transformcoefficients outputted by the orthogonal transform means, and theaverage value.

[0061] An image data decoding system adapted to the image data codingsystem, according to the second aspect of the present invention,comprises:

[0062] a first decoding means for decoding a coded map signal indicativeof the position and shape of a content in a screen inputted for everysquare block of picture signals to be coded;

[0063] a resolution transform means for performing the resolutiontransform of the map signal decoded by the first decoding means;

[0064] a second decoding means for decoding coded orthogonal transformcoefficients and an average value of pixels inside of the content;

[0065] a coefficient selecting means for selecting an orthogonaltransform coefficient necessary to reproduce an image of a predeterminedresolution, from the orthogonal transform coefficients decoded by thesecond decoding means, on the basis of the map signalresolution-transformed by the resolution transform means;

[0066] an inverse orthogonal transform means for performing thetwo-dimensional inverse orthogonal transform of the orthogonal transformcoefficient selected by the coefficient selecting means; and

[0067] a reproducing means for deriving a resolution-transformedregenerative picture signal by synthesizing the results of thetwo-dimensional inverse orthogonal transform by the inverse orthogonaltransform means, with the average value decoded by the second decodingmeans, on the basis of the map signal resolution-transformed by theresolution transform means.

[0068] According to a third aspect of the present invention, an imagedata coding system comprises:

[0069] a first coding means for coding a map signal indicative of theposition and shape of a content in a screen inputted for every squareblock of picture signals to be coded;

[0070] an average value inserting means for replacing the values ofpixels outside of the content, by an average value of the values ofpixels inside of the content in accordance with the map signal, withrespect to the blocks containing the boundary portion of the content inthe picture signals;

[0071] an orthogonal transform means for performing the two-dimensionalorthogonal transform of the signals of the average value in the blocksproduced by the average value inserting means, to output orthogonaltransform coefficients; and

[0072] a second coding means for coding the orthogonal transformcoefficients outputted by the orthogonal transform means.

[0073] In this case, in the average value inserting means, the values ofpixels outside of the content may be predicted under the condition thatthe average value of the pixels outside of the content coincides withthe average value of the pixels inside of the content.

[0074] An image data decoding system adapted to the image data codingsystem, according to the third aspect of the present invention,comprises:

[0075] a first decoding means for decoding a coded map signal indicativeof the position and shape of a content in a screen inputted for everysquare block of picture signals;

[0076] a resolution transform means for performing the resolutiontransform of the map signal decoded by the first decoding means;

[0077] a second decoding means for decoding coded orthogonal transformcoefficients;

[0078] a coefficient selecting means for selecting an orthogonaltransform coefficient necessary to reproduce an image of a predeterminedresolution, from the orthogonal transform coefficients decoded by thesecond decoding means, on the basis of the map signalresolution-transformed by the resolution transform means;

[0079] an inverse orthogonal transform means for performing thetwo-dimensional inverse orthogonal transform of the orthogonal transformcoefficient selected by the coefficient selecting means; and

[0080] a reproducing means for deriving a resolution-transformedregenerative picture signal by taking out the values of pixels inside ofthe content, with respect to the blocks containing the boundary portionof the content, on the basis of the map signal resolution-transformed bythe resolution transform means.

[0081] According to a fourth aspect of the present invention, an imagedata coding system comprises:

[0082] a first coding means for coding a map signal indicative of theposition and shape of a content in a screen inputted for every squareblock of picture signals to be coded;

[0083] a vector quantizing means for performing the matching of thepicture signal with code vectors stored in a code book and foroutputting an index indicative of a code vector which has the highestcorrelation to the picture signal; and

[0084] a second coding means for coding the index outputted by thevector quantizing means,

[0085] wherein the vector quantizing means for performing the matching,with the code vectors, only the signals inside of the content withrespect to the blocks containing the boundary portion of the content, inaccordance with the map signal.

[0086] An image data decoding system adapted to the image data codingsystem, according to the fourth aspect of the present invention,comprises:

[0087] a first decoding means for decoding a coded map signal indicativeof the position and shape of a content in a screen inputted for everysquare block of picture signals to be coded;

[0088] a resolution transform means for performing the resolutiontransform of the map signal decoded by the first decoding means;

[0089] a second decoding means for decoding a coded index; and

[0090] an inverse vector quantizing means, having a code book storingtherein code vectors indicated by multiple resolutions, for outputting acode vector designated by the index decoded by the second decodingmeans,

[0091] wherein the inverse vector quantizing means derives aresolution-transformed regenerative picture signal by taking out onlythe signals inside of the content with respect to the blocks containingthe boundary portion of the content, from the code vectors in accordancewith the map signal resolution-transformed by the resolution transformmeans.

[0092] According to a fifth aspect of the present invention, an imagedata coding system comprises:

[0093] a first coding means for coding a map signal indicative of theposition and shape of a content in a screen inputted for every squareblock of picture signals to be coded;

[0094] a subband dividing means for dividing the picture signal into aplurality of subband picture signals;

[0095] a resolution transform means for performing the resolutiontransform of the map signal into the resolution of each of the subbandpicture signals divided by the subband dividing means; and

[0096] a second coding means for coding each of the subband picturesignals divided by the subband dividing means,

[0097] wherein the second coding means codes only the signals inside ofthe content with respect to the block containing the boundary portion ofthe content in the subband picture signals, in accordance with the mapsignal resolution-transformed by the resolution transform means.

[0098] An image data decoding system adapted to the image data codingsystem, according to the fifth aspect of the present invention,comprises:

[0099] a first decoding means for decoding a coded map signal indicativeof the position and shape of a content in a screen inputted for everysquare block of picture signals to be coded;

[0100] a resolution transform means for performing the resolutiontransform of the map signal decoded by the first decoding means, intothe resolutions of a plurality of subband picture signals;

[0101] a second decoding means for decoding a plurality of coded subbandsignals; and

[0102] a subband synthesizing means for deriving aresolution-transformed regenerative picture signal by synthesizing onlythe subband picture signals necessary to reproduce an image of apredetermined resolution among the plurality of subband picture signalsdecoded by the second decoding means,

[0103] wherein the second decoding means decodes only the subbandpicture signals inside of the content with respect to the blockscontaining the boundary portion of the content among the subband picturesignals, in accordance with the map signal resolution-transformed by theresolution transform means.

[0104] In an image data coding and/or decoding system, according to thefirst aspect of the present invention, it is possible to code transformcoefficients and a map signal in a coding system, by performing thetwo-dimensional orthogonal transform of the picture signals of all thepixels with respect to the blocks (inside blocks) located inside of acontent, and of only the picture signals of pixels contained in thecontent with respect to the blocks (edge blocks) containing the boundaryportion of the content, in accordance with a map signal indicative ofthe position and shape of the content. It is also possible to performthe resolution transform with respect to the edge blocks containing acontent of an optional shape in a decoding system, by selecting anorthogonal transform coefficient necessary to reproduce an image of adesired resolution from decoded orthogonal transform coefficients on thebasis of a decoded and resolution-transformed map signal, and byperforming the two-dimensional orthogonal transform of all thecoefficients with respect to the inside blocks and of only thecoefficients contained in the content with respect to the edge blocks,respectively.

[0105] In this case, it is designed to be able to switch the order ofthe one-dimensional orthogonal transform in the horizontal and verticaldirections in the two-dimensional orthogonal transform, to detect thecorrelation in the horizontal and vertical directions of the picturesignals inside of the content, for performing, first, theone-dimensional orthogonal transform with respect to the directionhaving higher correlation, so that it is possible to improve the codingefficiency.

[0106] In an image data coding and/or decoding system, according to thesecond aspect of the present invention, in a coding system, by coding amap signal, outputting an average value of the values of pixels insideof a content with respect to blocks containing the boundary portion ofthe content among picture signals in accordance with the map signal,separating the average value from the values of pixels inside of thecontent, and setting the values of pixels outside of the content to bezero, to perform the two-dimensional orthogonal transform of the signalsfrom which the average value has been separated, it is possible to codethe orthogonal transform coefficients and the average value. In adecoding system, by selecting an orthogonal transform coefficientnecessary to reproduce an image of a desired resolution from decodedorthogonal transform coefficients on the basis of a decoded andresolution-transformed map signal, and deriving a resolution-transformedregenerative picture signal by synthesizing the results of thetwo-dimensional inverse orthogonal transform with the decoded averagevalue of the values of pixels inside of the content, it is possible toperform the resolution transform with respect to the edge blockscontaining a content of an optional shape. In addition, it is possibleto enhance the coding efficiency in the edge blocks by separating theaverage value inside of the content from the average value outsidethereof for coding.

[0107] In an image data coding and/or decoding system, according to thethird aspect of the present invention, a coding system can code a mapsignal, replace the values of pixels outside of a content by the averagevalue of the values of pixels inside of the content with respect toblocks containing the boundary portion of the content among the picturesignals in accordance with a map signal, output the replaced values, andperform the two-dimensional orthogonal transform of the signal of theaverage value in the block to code its orthogonal transform coefficient.In addition, a decoding system can select an orthogonal transformcoefficient necessary to reproduce an image of a predeterminedresolution from coded orthogonal transform coefficients on the basis ofa coded and resolution-transformed map signal, and take out the valuesof pixels inside of the content with respect to the edge blocks on thebasis of the results of the two-dimensional orthogonal transform toderive a resolution-transformed regenerative picture signal, so that itis possible to perform the resolution transform with respect to the edgeblocks containing a content of an optional shape.

[0108] In an image data coding and/or decoding system, according to thefourth aspect of the present invention, a coding system can code a mapsignal, perform the matching only the signals inside of a content with acode vector with respect to the edge blocks in accordance with the mapsignal, perform the vector quantization, and code an index indicative ofthe code vector of the highest correlation. In addition, in a decodingsystem, when performing the inverse vector quantization of the codevector designated by the decoded index, only the signals inside of thecontent are taken out from the code vector with respect to the edgeblocks in accordance with a decoded and resolution-transformed mapsignal, to derive a resolution-transformed regenerative picture signal,so that it is possible to perform the resolution transform with respectto the edge blocks containing a content of an optional shape.

[0109] In an image data coding and/or decoding system, according to thefifth aspect of the present invention, when picture signals are dividedinto subbands to be coded in a coding system, only the signals inside ofa content with respect to the edge blocks in subband picture signals arecoded in accordance with a map signal resolution-transformed intoresolutions of subband picture signals. In addition, in a decodingsystem, when subband-synthesizing only the subband picture signalnecessary to derive a regenerative picture signal of a predeterminedresolution, only the signals inside of the content with respect to theedge blocks among the subband picture signals are decoded in accordancewith a map signal resolution-transformed into the resolution of each ofthe subband picture signals, so that it is possible to perform theresolution transform with respect to the edge blocks containing acontent of an optional shape.

[0110] According to the present invention, a method for performing thetwo-dimensional orthogonal transform and/or the inverse orthogonaltransform for blocks of an optional shape is provided. That is, atwo-dimensional orthogonal transform method, according to the presentinvention, comprises:

[0111] a first transform step for performing the one-dimensionalorthogonal transform in the horizontal direction in accordance with amap signal indicative of the shape of a block inputted, and forperforming the rearrangement in order of the lower of coefficients inthe horizontal direction; and

[0112] a second transform step for performing the one-dimensionalorthogonal transform in the vertical direction in accordance with themap signal, and for performing the rearrangement in order of the lowerof coefficients in the vertical direction,

[0113] wherein with respect to a signal of an optional shape, the secondtransform step is performed after performing the first transform step,or the first transform step is performed after performing the secondtransform step.

[0114] According to the present invention, a two-dimensional inverseorthogonal transform method adapted to the aforementionedtwo-dimensional orthogonal transform method, comprises

[0115] a resolution transform step for performing the resolutiontransform of an input map signal;

[0116] a coefficient selecting step for selecting an orthogonaltransform coefficient necessary to reproduce an image of the resolutionin accordance with a resolution-transformed map signal;

[0117] a first inverse transform step for performing the one-dimensionalorthogonal transform in the vertical direction with respect to theselected orthogonal transform coefficient, and for performing therearrangement in the vertical direction; and

[0118] a second inverse transform step for performing theone-dimensional orthogonal transform in the horizontal direction withrespect to the selected orthogonal transform coefficient, and forperforming the rearrangement in the horizontal direction,

[0119] wherein a resolution-transformed signal of a block of an optionalshape is reproduced by performing the first inverse transform step priorto the second inverse transform step when the first transform step isperformed prior to the second transform step, and by performing thesecond inverse transform step prior to the first inverse transform stepwhen the second transform step is performed prior to the first transformstep.

BRIEF DESCRIPTION OF THE DRAWINGS

[0120] The present invention will be understood more fully from thedetailed description given hereafter and from the accompanying drawingsof the preferred embodiments of the invention. However, the drawings arenot intended to imply limitation of the invention to a specificembodiment, but are for explanation and understanding only.

[0121] In the drawings:

[0122]FIG. 1 is a block diagram showing a basic concept of an image datacoding system, according to the present invention;

[0123]FIG. 2 is a block diagram showing the detail structure of a codingmeans of an image data coding system, according to the presentinvention;

[0124]FIG. 3 is a schematic block diagram of the first preferredembodiment of an image data coding system, according to the presentinvention;

[0125]FIG. 4 is a view explaining the state of the distribution ofclosely observed points in the first preferred embodiment of an imagedata coding system, according to the present invention;

[0126] FIGS. 5(a) and 5(b) are views explaining the control of thecoding in accordance with the distribution of regions in the firstpreferred embodiment of an image data coding system, according to thepresent invention;

[0127]FIG. 6 is a view explaining the control of the coding ofcoefficient by the subband coding in the first preferred embodiment ofan image data coding system, according to the present invention;

[0128] FIGS. 7(a) and 7(b) are views explaining the state that thequantization characteristic is changed by changing the dead zone of aquantizer in the first preferred embodiment of an image data codingsystem, according to the present invention;

[0129]FIG. 8 is a schematic block diagram of the second preferredembodiment of an image data coding system, according to the presentinvention;

[0130]FIG. 9 is a detailed block diagram of a space-time filter in thesecond preferred embodiment of an image data coding system, according tothe present invention;

[0131] FIGS. 10(a) and 10(b) are views showing pixels being objects ofthe space filter processing by the space-time filter in the secondpreferred embodiment of an image data coding system, according to thepresent invention;

[0132]FIG. 11 is a schematic block diagram of the third preferredembodiment of an image data coding system, according to the presentinvention;

[0133]FIG. 12 is a schematic block diagram of the fourth preferredembodiment of an image data coding system, according to the presentinvention;

[0134] FIGS. 13(a) to 13(c) are views explaining the processing ofassignment of the code amount in the fourth preferred embodiment of animage data coding system, according to the present invention;

[0135]FIG. 14 is a schematic block diagram of the fifth preferredembodiment of an image data coding system, according to the presentinvention;

[0136]FIG. 15 is a schematic block diagram of the sixth preferredembodiment of an image data coding system, according to the presentinvention;

[0137]FIG. 16 is a schematic block diagram of the seventh preferredembodiment of an image data coding system, according to the presentinvention;

[0138]FIG. 17 is a schematic block diagram of the eighth preferredembodiment of an image data coding system, according to the presentinvention;

[0139]FIG. 18 is a schematic block diagram of the ninth preferredembodiment of an image data coding system, according to the presentinvention;

[0140]FIG. 19 is a block diagram of the tenth preferred embodiment of animage data coding system, according to the present invention;

[0141]FIG. 20 is a block diagram of an image data coding system in thefirst preferred embodiment of an image data coding and/or decodingsystem, according to the present invention;

[0142]FIG. 21 is a block diagram of an orthogonal transform circuit inFIG. 20;

[0143]FIG. 22 is a block diagram of an inverse orthogonal transform inFIG. 20;

[0144]FIG. 23 is a block diagram of an AS-DCT circuit in FIG. 21;

[0145]FIG. 24 is a block diagram of an AS-IDCT circuit in FIG. 21;

[0146]FIG. 25 is a view showing a transform method for the AS-DCT;

[0147]FIG. 26 is a block diagram of an image data decoding system in thefirst preferred embodiment of an image data coding and/or decodingsystem, according to the present invention;

[0148]FIG. 27 is a view showing a resolution transform method in thefirst preferred embodiment of an image data coding and/or decodingsystem, according to the present invention;

[0149]FIG. 28 is a block diagram of an image data coding system in thesecond preferred embodiment of an image data coding and/or decodingsystem, according to the present invention;

[0150]FIG. 29 is a block diagram of an orthogonal transform circuit inFIG. 29;

[0151]FIG. 30 is a block diagram of an inverse orthogonal transformcircuit in FIG. 28;

[0152]FIG. 31 is a block diagram of an AS-DCT circuit in FIG. 29;

[0153]FIG. 32 is a block diagram of an AS-IDCT circuit in FIG. 30;

[0154] FIGS. 33(a) and 33(b) are view showing a switching operation of atransforming order for AS-DCT in the second preferred embodiment of animage data coding and/or decoding system, according to the presentinvention;

[0155]FIG. 34 is a block diagram of an image data decoding system in thesecond preferred embodiment of an image data coding and/or decodingsystem, according to the present invention;

[0156]FIG. 35 is a view showing an example of a method for determining ascan order in the first and second preferred embodiment of an image datacoding and/or decoding system, according to the present invention;

[0157]FIG. 36 is a block diagram of a scan order determining circuit foractualizing a scalable function in the AS-DCT;

[0158]FIG. 37 is a block diagram of an image data coding system in thethird preferred embodiment of an image data coding and/or decodingsystem, according to the present invention;

[0159]FIG. 38 is a view showing a method for separating an average valuein the image data coding system in FIG. 37;

[0160]FIG. 39 is a block diagram of an image data decoding system in thethird preferred embodiment of an image data coding and/or decodingsystem, according to the present invention;

[0161]FIG. 40 is a view showing a method for synthesizing an averagevalue in the image data decoding system of FIG. 39;

[0162]FIG. 41 is a block diagram of an image data coding system in thefourth preferred embodiment of an image data coding and/or decodingsystem, according to the present invention;

[0163]FIG. 42 is a view showing a method for inserting an average valuein the image data coding system of FIG. 41;

[0164]FIG. 43 is a block diagram of an image data decoding system in thefourth preferred embodiment of an image data coding and/or decodingsystem, according to the present invention;

[0165]FIG. 44 is a view showing a method for separation of pixels in theimage data decoding system of FIG. 43;

[0166]FIG. 45 is a block diagram of an image data coding system in thefourth preferred embodiment of an image data coding and/or decodingsystem, according to the present invention;

[0167]FIG. 46 is a view explaining a method for the vector quantizationof a block of an optional shape in a vector quantizer of FIG. 45;

[0168]FIG. 47 is a view explaining a method for the inverse vectorquantization of a block of an optional shape in an inverse quantizer ofFIG. 45;

[0169]FIG. 48 is a block diagram of an image data decoding system in theforth preferred embodiment of an image data coding and/or decodingsystem, according to the present invention;

[0170]FIG. 49 is a view showing a code block provided in the inversevector quantizer of FIG. 48;

[0171]FIG. 50 is a view explaining the subband division of a picturesignal in the fifth preferred embodiment of an image data coding and/ordecoding system, according to the present invention;

[0172]FIG. 51 is a view showing the arrangement of the respectivecomponents on the axes when a picture signal is divided into foursubbands in the fifth preferred embodiment;

[0173]FIG. 52 is a block diagram of an image data coding system in thefifth preferred embodiment of an image data coding and/or decodingsystem, according to the present invention;

[0174]FIG. 53 is a block diagram of an image data decoding system in thefifth preferred embodiment of an image data coding and/or decodingsystem, according to the present invention;

[0175]FIG. 54 is a view showing an example of an image transmittingsystem to which an image data coding system and an image data decodingsystem, according to the present invention, are applied;

[0176]FIG. 55 is a view explaining the principle of a conventional imagedata coding system;

[0177]FIG. 56 is a view explaining a method for separating a picturesignal into a background and a content for coding;

[0178]FIG. 57 is a view explaining a conventional content-based coding;

[0179] FIGS. 58(a) and 58(b) are views explaining a conventional methodof the orthogonal transform of an optional shape; and

[0180]FIG. 59 is a view explaining a method for actualizing theresolution transform using the orthogonal transform.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0181] Referring now to the accompanying drawings, the preferredembodiments of the present invention will be described in detail below.

[0182]FIG. 1 is a block diagram showing the basic concept of the presentinvention. In this drawing, the reference numeral 1 denotes an inputterminal for inputting an image data signal, 3 denotes an screen-areadetermining means for determining the area of the produced screen byanalyzing the image data signal S1 inputted through the terminal 1 or byexternally manual operations, 4 denotes a code amount assigning controlmeans for outputting a control signal S2 which controls the assignmentof the code amount using a weight function corresponding to the area ofthe screen on the basis of the determined results from the screen-areadetermining means 3, and 10 denotes a coding means for coding the imagedata signal S1 inputted using the control signal S2 from the code amountassigning control means.

[0183]FIG. 2 is a detailed block diagram of the coding means 10 ofFIG. 1. The image data signal S1 is supplied to a motion-vectordetection circuit 11, a differential circuit 12 and a mode determiningcircuit 13. The coding means 10 further comprises: a reference framememory 14, having variable delay function for motion-compensation, forstoring a reference frame; a selector 15 for outputting an input signalor a differential signal; a selector 16 for outputting a signal of zerolevel or a motion-compensation signal; a DCT circuit 17 for performingthe discrete cosine transform (DCT) of the output from the selector 15;and a quantization and inverse quantization means 20 for performing thequantization and inverse quantization processing of the output from theDCT circuit 17 in accordance with the weighting by the inputted controlsignal S2; an inverse DCT circuit 18 for performing the inverse discretecosine transform of the output from the quantization and inversequantization means 20; and an addition circuit 19 for adding the outputsfrom the selector 16 and the inverse quantization circuit 18. Thequantization and inverse quantization means 20 comprises a quantizationcircuit 21 and an inverse quantization circuit 22.

[0184] With this construction, the motion-vector detecting circuit 11detects a motion-vector between the reference frame stored in thereference frame memory 14 having the variable delay function formotion-compensation, and the inputted image data signal S1, for everymicroblock (MB) composed of 16×16 pixels.

[0185] The differential circuit 12 derives a difference between themotion-compensation signal S3 of the reference frame outputted from thereference frame memory 14, and the inputted image data signal S1, tosupply the difference to the mode determining circuit 13 and theselector 15.

[0186] The mode determining circuit 13 compares the differential signalS4 outputted from the differential circuit 12 with the AC component ofthe inputted image data signal, to determine as to whether theintraframe or interframe coding of the block is performed. Thedetermined results are supplied to the selector 15 and the selector 16via the selector 15.

[0187] The selector 15 selects the inputted image data signal S1 when itis determined to perform the intraframe coding, and the differentialsignal S4 when it is determined to perform the interframe coding, tosupply a selected signal S5 to the DCT circuit 17.

[0188] The DCT circuit 17 transforms the selected signal S5 into thediscrete cosine transform coefficient S6, to supply it for thequantization and inverse quantization means 20.

[0189] The quantization and inverse quantization means 20 quantizes thediscrete cosine transform coefficient S6 supplied from the DCT circuit17, in accordance with the control signal S2 relating to thequantization step size supplied for the quantization circuit 21 from arate control circuit (not shown) of the code amount assigning controlmeans, to output a transform coefficient signal S7. This quantizationsignal S7 is also supplied to the inverse quantization circuit 22, sothat the inverse quantization circuit 22 performs the inversequantization of the transform coefficient signal S7 into the discretecosine transform coefficient S6 in accordance with the control signal S2relating to the quantization step size.

[0190] The inverse DCT circuit 18 performs the discrete cosine inversetransforms of the discrete cosine transform coefficient S6 formed by theinverse quantization, to reproduce any signals selected by the selector15. That is, when it is determined to perform the intraframe coding, asignal corresponding to the image data signal S1 is reproduced, and whenit is determined to perform the interframe coding, a signalcorresponding to the differential signal S4 is reproduced. The signalproduced by the inverse transform by the inverse DCT transform circuit18 is supplied to the addition circuit 19.

[0191] On the other hand, the selector 16 selects the signal of zerolevel when the mode determined by the mode determining circuit 13 is theintraframe coding, and it selects the motion-compensation estimatingsignal S3 stored in the reference frame memory 14 when the mode is theinterframe coding, to supply the selected signal to the addition circuit19. The addition circuit 19 adds the output of the selector 16 to theoutput of the inverse DCT circuit 18, to supply it to the referenceframe memory 14. The reference frame memory 14 stores therein theaddition signal outputted from the addition circuit 19, and supplies isthe reference frame signal when the motion-vector detection circuit 11performs the motion-vector detection.

[0192] Furthermore, the transform coefficient S7 quantized by thequantization circuit 21 is variable-length coded with side informationsuch as motion-vector, and then, it is multiplexed to be outputted.

[0193] Referring to FIGS. 3 to 7, the first preferred embodiment of animage data coding system, according to the present invention, will bedescribed below.

[0194] In FIG. 3, an encoder 25 for coding the input image data S1 isprovided between the input terminal 1 and the output terminal 2. Theimage data signal S1 is also supplied to the resolution detectingcircuit 23 serving as the screen-area determining means 3. Theresolution detecting circuit 23 detects the resolution (the number ofpixels) of the input image data signal, to supply information on thenumber of pixels to the code-amount assigning control circuit 24.

[0195] The code-amount assigning control circuit 24 first varies theweight distribution function for assigning the code amount correspondingto the position in the screen in accordance with the number of thepixels in the input image. The weight distribution function for theassignment of the code amount may be the standard deviation of atwo-dimensional normal distribution as a function of the number ofpixels, as shown in FIG. 5.22 of the aforementioned literature“Estimation Technique of Image Quality and Tone Quality”. FIG. 4 is arewritten view of FIG. 5.22 of the aforementioned literature, and showsthe relationship between the distribution of closely observed points 27in a contour 26 of a screen in a current television system, and thedistribution of closely observed points 29 in a contour 28 of a screenin a high quality television system. As can be clearly seen from thisdrawing, the distribution of closely observed points extends as the sizeof the screen increases. Therefore, the two-dimensional normaldistribution of closely observed points can be applied to the weightdistribution function as a function of the number of pixels.

[0196] As shown in FIGS. 5(a) and 5(b), the weight distribution functionfor the assignment of the code amount may switch the weight for everyregion divided into microblocks (MB). That is, in FIG. 5(a), the blocksdivided by dotted lines are microblocks (MB), the weighting is performedso that the produced coded-amount of the region 31 is less than that ofthe region 32. This distribution function is set so that the weight ofthe central portion of the screen for the image having a less number ofpixels as shown in FIG. 5(a) is greater than that for the image having amore number of pixels as shown in FIG. 5(b). The weight distributionfunction thus set is supplied to the encoder 25.

[0197] In accordance with the distribution function for the assignmentof the code amount supplied by the code-amount assigning control circuit24, the encoder 25 performs the weighting of the code amount produced byvarying the quantization characteristic in accordance with the positionof the pixel or the position of the block on the screen in thequantization and inverse quantization circuit 20.

[0198] As a first method for varying the quantization characteristic, inthe coding using the orthogonal transform and the subband coding, withrespect to the first regions 31 and 33 located on the periphery of FIGS.5(a) and 5(b), the coefficient of a higher frequency component than thatof the boundary b1 of FIG. 6 is not compulsorily coded, and with respectto the second regions 32 and 34 located at an intermediate portion, thecoefficient of a higher frequency component than that of the boundary b2is not compulsorily coded.

[0199] In a second method for varying the quantization characteristic,the quantization matrix weighted for every transform coefficient isswitched between the first and second regions 31 and 32 of FIG. 5(a) orbetween the first and second regions 33 and 34 of FIG. 5(b).

[0200] In a third method for varying the quantization characteristic, asshown in FIG. 7, the dead zone of the quantizer is changed. In FIG. 7,the reference numeral 35 denotes a dead zone, and 36 denotes typicalvalues of quantization.

[0201] Referring to FIGS. 8 to 10, the second preferred embodiment of animage data coding system, according to the present invention, will bedescribed in detail below.

[0202] The image data signal S1 is supplied to the frame memory 38. Thisframe memory 38 supplies an image signal S8 of the current frame to aresolution detecting circuit 23 and a space-time filter 40, and an imagesignal S9 of the previous frame only to the space-time filter 40.

[0203]FIG. 9 shows the detailed structure of the space-time filter 40.As shown in FIG. 9, the space-time filter 40 comprises an intraframefilter circuit 41 for performing the space filter processing of theimage signal SB of the current frame, a multiplication circuit 42 formultiplying the output of the filter circuit 42 in the frame by k, amultiplication circuit 43 for multiplying the image signal S9 of theinputted previous frame by “1−k”, and an addition circuit 44 for addingthe multiplied outputs of the multiplication circuits 42 and 43.

[0204] In a case where the output *X of a pixel X shown in each of FIGS.10(a) and 10(b) is derived from the intraframe filter circuit 41 of thespace-time filter 40, an example of operation formula is as follows.

*X=(A+mB+C+mD+mE+F+mG+H+m2X)/(m+2)2

[0205] wherein m is a variable for varying the strength of the spacefilter.

[0206] The output *X of the intraframe space filter circuit 41 ismultiplied by k by means of the multiplication circuit 42, to be addedin the addition circuit 44 to the value derived by multiplying the inputimage signal P of the previous frame by “1−k” by means of themultiplication circuit 42, so that the time filter processing is carriedout. The aforementioned k is a coefficient for varying the strength ofthe time filter. Furthermore, FIG. 10(a) is a view showing therelationship between the positions of the pixel X and P. Thecoefficients m and k are set so that the value of coefficient in thefirst region 31 of FIG. 5(a) is less than that in the second region 32thereof, in accordance with the code-amount weight distribution functioncontained in the control signal S2 supplied from the code-amountassigning control circuit 24. In this way, the space-time filtering tothe image signal of the first region 31 is strengthly performed, so thatit is possible to restrain the produced code amount. The output of thespace-time filter 40 is supplied to the encoder 25 as a signal S10, andcoded here to be outputted to the outside via the output terminal 2.

[0207] Referring to FIG. 11, the third preferred embodiment of an imagedata coding system, according to the present invention will be describedbelow.

[0208] The third preferred embodiment of an image data coding system isdifferent from the second preferred embodiment of the system as shown inFIG. 8, at the points that the encoder 25 in the second preferredembodiment of the image data coding system comprises the samequantization and inverse quantization circuit 20 as that in the firstpreferred embodiment of the image data coding system as shown in FIG. 3,and that the code-amount assigning weight distribution function is notonly supplied to the space-time filter 40, but also supplied to thequantization and inverse quantization circuit 20 of the encoder 25.

[0209] In FIG. 11, the coefficients m and k of the space-time filter 40are set so that the value of coefficient of the first region 31 of FIG.5 is less than that of the second region 32 thereof, in accordance withthe code-amount assigning weight distribution function contained in thecontrol signal S2 supplied from the code-amount assigning controlcircuit 24. In this way, the space-time filter processing of the firstregion 31 of FIG. 5 is stronger than that of the second region 32, sothat the code amount produced in the first region 31 can be restrained.

[0210] The output of the space-time filter 40 is supplied to the encoder25 as a signal S10, and coded to be outputted. In this encoder 25, sincethe code-amount assigning weight distribution function contained in thecontrol signal S2 supplied from the code-amount assigning controlcircuit 24 is also supplied to the quantization and inverse quantizationcircuit 20, the quantization and inverse quantization circuit 20performs the weighting of the produced code amount S0 as to vary thequantization characteristic in accordance with the positions of thepixels and the blocks on the screen, in the same manner as that of thefirst preferred embodiment. The image signal weighted so as to vary thequantization characteristic by the positions on the screen is coded withthe produced code amount which is different in accordance with thepositions, and then, outputted to the outside via the output terminal 2.

[0211] Referring to FIG. 12, the fourth preferred embodiment of an imagedata coding system, according to the present invention, will bedescribed below.

[0212] This fourth preferred embodiment of an image data coding systemis not provided with the space-time filter 40 in the third preferredembodiment of an image data coding system. In this embodiment, the imagesignal of the current frame of the frame memory 38 is supplied to theencoder 25, and the respective image signals of the current and previousframes are supplied to a face-region detecting circuit 45, so that thequantization characteristic of the quantization and inverse quantizationcircuit 20 is varied by a control signal S2 containing the code-amountassigning weight distribution function outputted from the code-amountassigning control circuit 24 which receives the output of theface-region detecting circuit 45 and the output of the resolutiondetecting circuit 23.

[0213] With the aforementioned construction, the face-region detectingcircuit 45 detects the face region in the same manner as that of “ImageData Coding System” disclosed in the aforementioned Japanese PatentFirst (unexamined) Publication No. 5-95541, and the detected results aresupplied to the code-amount assigning control circuit 24 as an outputsignal S11.

[0214] In the code-amount assigning control circuit 24, first, as shownin FIG. 13(a), the first region 31 and the second region 32 aredetermined in accordance with the number of pixels of the input image inthe same manner as that of the first preferred embodiment, to vary theweight function for the assignment of the code amount in accordance withthe positions on the screen. Then, the face region 47 of FIG. 13(b) isdetected, and the weight distribution function is modified as shown inFIG. 13(c) in view of the detected results of the face region 47. Anexample of a method for this modification is as follows.

[0215] The interior of the face region 47 of FIG. 13(c) is assumed to bea third region 53. A part of the second region 32 of FIG. 13(a) which isnot contained in the face region 47 of FIG. 13(c) becomes the secondregion 32. If a portion contained in the first region 31 of FIG. 13(l)is contained in the face region, this portion becomes the first region31. A portion contained in the second region 32 and contained in theface region 47 of FIGS. 13(b) and 13(c) serves as the third region 53 ofFIG. 13(c).

[0216] The weight distribution function as shown in FIG. 13(c) issupplied to the encoder 25.

[0217] In the encoder 25, in accordance with the code-amount assigningweight distribution function, the quantization and inverse quantizationcircuit 20 performs the weighting of the produced code amount by varyingthe quantization characteristic in accordance with the positions of thepixel and the block on the screen, in the is same manner as that of thefirst preferred embodiment.

[0218] Referring to FIG. 14, the fifth preferred embodiment of an imagedata coding system, according to the present invention, will bedescribed below.

[0219] This fifth preferred embodiment of an image data coding systemcomprises the combination of the second preferred embodiment of thesystem as shown in FIG. 8 with the fourth preferred embodiment of thesystem as shown in FIG. 12.

[0220] In FIG. 14, the image signal S8 of the current frame outputtedfrom the frame memory 38 is supplied to three circuits, i.e. theresolution detecting circuit 23, the space-time filter 40 and the faceregion detecting circuit 45. The image signal S9 of the last frame issupplied to both of the space-time filter 40 and the face regiondetecting circuit 45. The outputs of the resolution detecting circuit 23and the face region detecting circuit 45 are supplied to the code-amountassigning control circuit 24, so that the code-amount assigning weightdistribution function is set. On the basis of this weight distributionfunction, the space-time filter 40 performs the space-time filterprocessing for the image signals S8 and S9 of the current and previousframes, and outputs a signal S10 to the encoder 25. The encoder 25 codesthis signal S10 to output to the outside via the output terminal 2.

[0221]FIG. 15 is a block diagram showing the sixth preferred embodimentof an image data coding system, according to the present invention. Inthis sixth preferred embodiment, the encoder 25 in the fifth preferredembodiment corresponds to one comprising the quantization and inversequantization circuit 20 in the second preferred embodiment. Since othercomponents are the same as or correspond to the components having thesame reference numerals as those in some preferred embodiments asmentioned above, only such reference numerals are used in the drawing,and the repeated explanations are omitted.

[0222] The space-time filter 40 of FIG. 14 receives a control signal S2containing the code-amount assigning weight distribution functionsupplied from the code-amount assigning control circuit 24, and performsthe space-time filter processing to output a signal S10 to the encoder25.

[0223] In the encoder 25, in the weight distribution function containedin the control signal supplied from the code-amount assigning controlcircuit 24 in the same manner as that of the first preferred embodiment,the quantization and inverse quantization circuit 20 varies thequantization characteristic in accordance with the positions of thepixel and the block on the screen, to perform the weighting of theproduced code amount.

[0224]FIG. 16 is a block diagram showing the seventh preferredembodiment of an image data coding system, according to the presentinvention. In FIG. 16, the characterizing feature of this seventhpreferred embodiment is that a sink screen-size detecting circuit 50 isprovided for receiving an output signal from the frame memory 38 todetect the size of the sink screen, and that the code-amount assigningcontrol circuit 24 derives the code-amount assigning weight distributionfunction on the basis of both of the output signals of the sinkscreen-size detecting circuit 50 and the frame memory 38, and thederived function is supplied to the quantization and inversequantization circuit 20 of the encoder 25. In a case where thespace-time filter is provided, the same operation as that of thepreferred embodiment of an image data coding system is performed, sothat the repeated explanations are omitted.

[0225]FIG. 17 is a block diagram showing the eighth preferred embodimentof an image data coding system, according to the present invention.

[0226] In this drawing, the same face-region detecting circuit 45 asthat in the fourth preferred embodiment as shown in FIG. 12 is providedin addition to the structures in the seventh preferred embodiment asshown in FIG. 16. To the code-amount assigning control circuit 24, theoutput of the face-region detecting circuit 45 in addition to the outputof the sink screen-size detecting circuit 50 are supplied. Therefore, onthe basis of the output of the sink screen-size detecting circuit 50 andthe output of the face-region detecting circuit 45, the code-amountassigning control circuit 24 sets the code-amount assigning weightdistribution function by the image data inputted through the framememory 38, to output it to the quantization and inverse quantizationcircuit 20 of the encoder 25. The quantization and inverse quantizationcircuit 20 varies the quantization characteristic on the basis of thesupplied distribution function, and performs the weighting of theproduced code amount to output a signal to the outside via the terminal2.

[0227] In the seventh and eighth preferred embodiments of an image datecoding system, according to the present invention, it is possible toeasily detect, on the sink, the size of the screen of the receivedinformation to be reproduced, the information being transmitted bytransmitting the header information indicative of the size of the screenand so forth in addition to the image data signal.

[0228] In the seventh and eighth preferred embodiments of an image datacoding system as shown in FIGS. 16 and 17, the size of the screen isinternally and automatically detected on the sink to be controlled, bythe sink screen-size detecting circuit 50 serving as means for detectingthe size of the screen supplied to the code-amount assigning controlcircuit 24. However, the present invention is not limit to thisstructure, but the weighting of the produced code amount may beperformed by input in an externally manual operation.

[0229] That is, the ninth and tenth preferred embodiments of image datacoding systems, as shown in FIGS. 18 and 19, according to the presentinvention, may be applied.

[0230]FIG. 18 is a schematic view of the ninth preferred embodiment ofan image data coding system, according to the present invention. Thisninth preferred embodiment of an image data coding system does notdetect the size of the screen of the received information in the sinkscreen-size detecting circuit 50 in the seventh preferred embodiment ofthe image data coding system, and a screen-size setting means 55 isprovided for setting the size of the screen in an externally manualoperation. The screen-size setting means 55 does not detect theresolution of the received image data signal, the header informationindicative of the area and so forth, to derive the size of the screen,but is designed so as to input the size of the received screen to thesink system in a manual operation. The information signal on the inputscreen-size is supplied to the code-amount assigning control circuit 24of the coding system via an input terminal 56. The other constructionsare the same as those of the seventh preferred embodiment.

[0231] Similar to the ninth preferred embodiment, the tenth preferredembodiment of an image data coding system as shown in FIG. 19 has thescreen-size setting means 55 and the input terminal for inputting theinformation signal on the size of the received screen manually inputtedvia the input terminal 56. Since the other constructions are the same asthose of the eighth preferred embodiment as shown in FIG. 17, therepeated explanations are omitted.

[0232] As mentioned above, an image data coding system, according to thepresent invention, includes a screen-area determining means which canautomatically or manually set the area of the reproduced screen.Specifically, the screen-area determining means can analyze theresolution for analyzing the number of pixels, designate the size of thescreen by the header information, set the size of the screen in a manualoperation and so forth. Therefore, it is possible to improve the codingefficiency by reproducing the image after weighting in accordance withthe distribution of the closely observed points in view of human'svisual characteristic.

[0233] As mentioned above, an image data coding system, according to thepresent invention, was made by turning the inventor's attention that, inhuman's visual characteristic, the distribution of the closely observedpoints does not 80 diffuse when the object to be visually recognized issmall, and it is designed to vary the assignment of the code amount onthe respective regions on the screen without varying the code amount onthe whole reproduced screen when the size of the screen is small.Therefore, it is possible to subjectively improve the picture quality ofthe reproduced image.

[0234] Referring to the drawings, particularly to FIGS. 20 to 54, thepreferred embodiments of an image data coding and/or decoding system,according to the present invention, will be described below.

[0235] (First Preferred Embodiment)

[0236]FIG. 20 is a block diagram of the first preferred embodiment of animage data coding system, according to the present invention. An inputimage signal 10 is divided into a plurality of square blocks by ablocking circuit (not shown) to be supplied to a substraction circuit100. In the substraction circuit 100, a predicted error signal 30 whichis a difference between a motion-compensated prediction signal suppliedfrom a motion-compensated prediction circuit and the input image signal10, is derived to be supplied to an orthogonal transform circuit 200.

[0237] The orthogonal transform circuit 200 transforms the predictederror signal 30 into an orthogonal transform coefficient in accordancewith an alpha map signal 20 supplied block by block, and then, suppliesthe orthogonal transform coefficient to a quantization circuit 120. Thequantized coefficient by the quantization circuit 120 is coded by avariable length coding circuit 140, as well as is inversely quantized byan inverse quantization circuit 130. An inversely quantized transformcoefficient 40 is inversely transformed by an inverse orthogonaltransform circuit 300, and then, added to the motion-compensatedprediction signal, which is supplied from a motion-compensatedprediction circuit 110, in an addition circuit 150.

[0238] A local-decoded image signal which is the output of the additioncircuit 150, is stored in a frame memory in the motion-compensatedprediction circuit 110. The transform coefficient coded by the variablelength coding circuit 140, and the alpha map signal coded by an alphamap coding circuit 160, together with side information such asmotion-vector information, are multiplexed in a multiplexed circuit 170to be outputted as a code bit stream 50. Furthermore, the alpha mapsignal is coded by a method for coding a binary image, for example, byMMR (Modified Read).

[0239] The orthogonal transform circuit 200 and the inverse orthogonaltransform circuit 300 in FIG. 20 will be described in detail below.

[0240]FIGS. 21 and 22 are detailed block diagrams of the orthogonaltransform circuit 200 and the inverse orthogonal transform circuit 300,respectively.

[0241] The orthogonal transform circuit 200 as shown in FIG. 21comprises a switch circuit 210, an AS-DCT circuit 220 and a DCT circuit230. The alpha map signal 20 is supplied to both of the switch circuit210 and the AS-DCT circuit 220. The switch circuit 210 determines as towhether the block of the input predicted error signal 30 is an internalblock, an external block or an edge block as shown in FIG. 53, to supplythe predicted error signal 30 to the DCT circuit 230 when it is theinternal block, and the predicted error signal 30 to the AS-DCT circuit220 when it is the edge block, i.e. the block containing the boundaryportion of a content. Furthermore, when it is the external block, thecoding is not performed or is performed by the other method.

[0242]FIG. 23 is a block diagram of the AS-DCT circuit 220, and FIG. 25shows an example of a transform method in the AS-DCT. As shown in FIG.25, the pixels contained in a content expressed by slanting lines in theinput edge block are first put together to the left end by arearrangement circuit 221. Then, in a DCT circuit 222, with respect tothe pixels expressed by slanting lines, the one-dimensional DCT isperformed in the horizontal direction. Then, in a DCT circuit 224, thetransform coefficients expressed by a mesh are put together to the upperedge. Finally, in a DCT circuit 224, with respect to the transformcoefficients expressed by a mesh, the one-dimensional DCT is performedin the vertical direction. Furthermore, it is possible to change theorder of the rearrangement and DCT for processing.

[0243] The inverse orthogonal transform circuit 300 as shown in FIG. 22comprises a switch circuit 310, an AS-IDCT circuit 320 and an IDCTcircuit 330, and the alpha map signal 20 is supplied to both of theswitch circuit 310 and the AS-IDCT circuit 320.

[0244]FIG. 24 is a block diagram of the AS-IDCT circuit 320 whichcomprises an IDCT circuit 321, a rearrangement circuit 322, an IDCTcircuit 323 and a rearrangement circuit 324. Thus, in the inverseorthogonal transform circuit 300, the operation contrary to theorthogonal transform circuit 200 is performed.

[0245] An image data decoding system in this preferred embodiment willbe described below.

[0246]FIG. 26 is a block diagram of an image data decoding system havingthe resolution transform function corresponding to the image data codingsystem of FIG. 20. The input code bit stream 60 is separated into thecomponent of the transform coefficient and the alpha map signal in aseparating circuit 400. The code of the transform coefficient is decodedby a variable length decoding circuit 410, and then, is inverselyquantized by an inverse quantization circuit 420. On the other hand, thealpha map signal is decoded by an alpha map decoding circuit 430, andthen, is transformed into a desired resolution by a resolution transformcircuit 440.

[0247] The resolution transform circuit 440 performs the resolutiontransform of the alpha map signal which is a binary picture signal. Ansuch a method for performing the resolution transform of a binarypicture signal, for example, it is possible to use an enlargement andreduction method disclosed in “Image Processing Handbook” (p.630,Shokodo), which will be hereinafter referred to as “Literature 5”. In acoefficient selecting circuit 450, the alpha map signal, the resolutionof which is transformed in the resolution transform circuit 440, isrearranged in the horizontal direction, and then, in the verticaldirection, in the same transform method as that of the aforementionedAS-DCT, as shown in FIG. 27. Furthermore, FIG. 27 is an example in whichthe resolution is transformed into ⅝ in both of the horizontal andvertical directions.

[0248] Then, the coefficient of a required band is selected from thetransform coefficients supplied by the inverse quantization circuit 420,to be supplied to an inverse orthogonal transform circuit 460. In theinverse transform circuit 460, with respect to the transform coefficientof the internal block, the 5×5 of two-dimensional IDCT is performed, andwith respect to the transform coefficient of the edge block, the AS-IDCTis performed in accordance with the resolution-transformed alpha mapsignal supplied by the resolution transform circuit 440, so that theinversely transformed signal is supplied to an addition circuit 470. Theaddition circuit 470 outputs a regenerative signal derived by adding amotion-compensated prediction signal supplied from a motion compensationcircuit 480 to a signal supplied from the inverse orthogonal transformcircuit 460.

[0249] (Second Preferred Embodiment)

[0250] Referring to FIGS. 28 to 34, the second preferred embodiment ofan image data coding and/or decoding system, according to the presentinvention.

[0251]FIG. 28 is a block diagram of an image data coding system,according to the present invention. In this embodiment, an orthogonaltransform circuit 250 and an inverse orthogonal transform circuit 350comprise an As-DCT circuit and an AS-IDCT circuit which can switch theorders of the AS-DCT circuit 220 of FIG. 21 and the AS-IDCT circuit 320of FIG. 22, respectively. A correlation detecting circuit 180 detects acorrelation between the components of the predicted error signal 30 inthe horizontal and vertical directions, and supplies a signal (a switchsignal) 21 indicative of the direction of the high correlation to theorthogonal transform circuit 250, the inverse orthogonal transformcircuit 350 and the multiplexer circuit 170. As a method for detectingthe correlation in the correlation detecting circuit 180, for example,there is a method for deriving the square error between the adjacentpixels in the horizontal and vertical directions.

[0252]FIGS. 29 and 30 are detailed block diagrams of the orthogonaltransform circuit 250 and the inverse orthogonal transform circuit 350,respectively. Similar to FIG. 21, the orthogonal transform circuit 250as shown in FIG. 29 comprises a switch circuit 210, an AS-DCT circuit260 and a DCT circuit 230. The alpha map signal 20 is supplied to theswitch circuit 210 and the AS-DCT circuit 260, and the switching signal21 is supplied to the AS-DCT circuit 260. The inverse orthogonaltransform circuit 350 as shown in FIG. 30 comprises a switch circuit310, an AS-IDCT circuit 360 and an IDCT circuit 330. The alpha mapsignal 20 is supplied to the switch circuit 310 and the AS-IDCT circuit360, and the switching signal 21 is supplied to the IDCT circuit 330.

[0253]FIGS. 31 and 32 are block diagrams of the AS-DCT circuit 260 ofFIG. 29 and the AS-IDCT circuit 360 of FIG. 30, respectively. FIG. 33 isa view explaining, in detail, a method for switching the order oftransform in the AS-DCT circuit 260 and the AS-IDCT circuit 360. Theorder of transform is changed by switching first switch circuits 261,361 and second switch circuits 262, 362 of FIGS. 31 and 32, in themanner as shown in FIGS. 33(a) and 33(b). Specifically, by means of theswitching signal 21, the switch circuits 261, 262 are switched as shownin FIG. 33(a) when the correlation in the horizontal direction is high,and as shown in FIG. 33(b) when the correction in the vertical directionis high. Furthermore, the switching signal 21 may be coded with one bitblock by block or with one bit by frame by frame.

[0254] An image data decoding system, according to the presentinvention, will be described below.

[0255]FIG. 34 is a block diagram of an image data decoding system havingthe resolution transform function corresponding to the image codingsystem of FIG. 28. The point different from the first preferredembodiment of an image data decoding system as shown in FIG. 26 is thata transform order switching signal 61 separated from an input coding bitstream 60 in the separating circuit 400 is supplied to an inverseorthogonal transform circuit 461. The inverse orthogonal transformcircuit 461 is the same as the inverse orthogonal transform circuit 350in the image data coding system as shown in FIG. 30, and switches theorder of transform by the switching signal 61 in the same manner as thatdescribed in FIG. 33.

[0256] Referring to FIGS. 35 and 36, an example of a method for scanningthe transform coefficient of the AS-DCT will be described below. Ingeneral, in a case where the DCT coefficient of a square block is coded,after zigzag scan, the synthesized phenomenon of the magnitude of thecoefficient and the zero run length is coded using the two-dimensionalvariable length coding (see “Image Coding Techniques—DCT and ItsInternational Standard—”, pp288-290). On the other hand, in the AS-DCT,due to the shape of the block, the distribution of the transformcoefficient is leaned in the horizontal direction h and the verticaldirection v as shown in FIG. 35. Therefore, according to this preferredembodiment, in both of the image data coding system and the image datadecoding system, the order of scan is determined so as to adapt to thedistribution of transform coefficients which can be specified by thealpha map signal.

[0257]FIG. 35 is an example of a method for determining the order ofscan. First, the alpha map signal 20 (0: Outside of Content, 1: Insideof Content) is rearranged in the horizontal direction h and the verticaldirection v to derive the distribution of transform coefficients (map[v][h]: v, h=0˜size-1). Then, in accordance with a method described byC-Language as follows, the order of scan (order [v][h]:v, h=0˜size-1) isdetermined.  cont = 0;  for (s=0; s<2*size−1; s⁺⁺) {   for (v= 0;v<size; v⁺⁺)   for (h= 0; h<size; h⁺⁺) {     sequ = i + j;    if (s ==seq && map [v][h]) {     cont++;     order [v][h] − cnt    }   } }

[0258] In addition, various scan methods for actualizing scalablefunction on coding data has been proposed (see “Image CodingTechniques”, FIG. 7.114).

[0259]FIG. 36 is a block diagram of a scan-method determining circuitfor actualizing scalable function in the AS-DCT. In the resolutiontransform circuit 440, the resolution transform of an alpha map signal80 is performed (for example, ½ in both of the horizontal and verticaldirections) to be supplied to a first horizontal and verticalrearrangement circuit 441. To a second horizontal and verticalrearrangement circuit 442, the alpha map signal 80, the resolutiontransform of which is not performed, is supplied. In the horizontal andvertical rearrangement circuits 441, 442, the rearrangement as shown inFIG. 35 is performed. As a result, (map [v][h]) is supplied to a firstscan-order determining circuit 444 and an exclusive OR operation circuit443.

[0260] In the first scan-order determining circuit 444, the scan order(the order of a low-band component) of the resolution transformed alphamap signal is determined in a manner of FIG. 35, and the information 81indicative of the scan order is supplied to a second scan-orderdetermining circuit 445. The exclusive OR operation circuit 443 derivesa difference between the map [v][h] of a low resolution supplied fromthe first horizontal and vertical rearrangement circuit 441 and the map[v][h] of a high resolution supplied from the second horizontal andvertical rearrangement circuit 442, and supplies this difference 82 tothe second scan-order determining circuit 445.

[0261] In the second scan-order determining circuit 445, the scan orderof a high-band component is determined subsequently to the scan order ofthe low-band component determined by the first scan-order determiningcircuit 444, and the information 83 indicative of the scan order of thecombination of the low and high band components is output. Thisalgorithm is applicable when more multistage division is performed todetermine the scan order.

[0262] (Third Preferred Embodiment)

[0263] Referring to FIGS. 37 to 40, the third preferred embodiment of animage data coding and/or decoding system, according to the presentinvention, will be described below.

[0264]FIG. 37 is a block diagram of an image data coding system in thisembodiment. In an average value separating circuit 500, if the predictederror signal 30 is an edge block signal in accordance with the alpha mapsignal 20, an average value of the signals inside of a content (theportion of oblique lines in FIG. 38) is derived to be separated, and allthe signals outside of the content is set to be zero. By thisprocessing, the average value in the central square blocks of FIG. 38becomes zero. When the signal 32 indicative of the average value 0 inthe blocks is supplied to the DCT circuit 230 for performing thetwo-dimensional DCT, the DC component becomes zero as the right-sidesquare blocks of FIG. 38. In this case, an extrapolated signal may besubstituted for the signals outside of the content under the conditionthat the average value is 0.

[0265] The average value 31 derived in the average value separatingcircuit 500, together with the alternating current transform coefficientof the DCT supplied from the DCT circuit, is supplied to a quantizationcircuit 121, and quantized to be supplied to an inverse quantizationcircuit 131 and a variable length coding circuit 140. In the inversequantization circuit 131, the average value and the alternating currenttransform coefficient are inversely quantized. A quantized average value41 is supplied to an average value synthesizing circuit 510, and aquantized alternating current transform coefficient 42 is supplied tothe inverse DCT circuit 330.

[0266] In the average value synthesizing circuit 510, a regenerativesignal is derived by synthesizing the signals inside of the content withthe average value 41 in accordance with the alpha map signal 20inversely transformed in the inverse DCT circuit 330. At this time, thesignals outside of the content are reset to be, for example, zero.

[0267] An image data decoding system in this embodiment will bedescribed below.

[0268]FIG. 39 is a block diagram of an image data decoding system havingthe resolution transform function corresponding to the image data codingsystem of FIG. 37, and FIG. 40 is a view showing a method forreproducing the signal that the resolution transform is performed. InFIG. 39, an inverse quantization circuit 421 inversely quantizes theaverage value and the alternating current transform coefficient, tosupply an average value 62 to an average value synthesizing circuit 511and an alternating current transform coefficient 63 to a coefficientselecting circuit 451, respectively. In an inverse DCT circuit 462, theDCT is performed with respect to the transform coefficient having a bandnecessary to derive a desired resolution selected in the coefficientselecting circuit 451 (in an example of FIG. 40, a 5×5 oftwo-dimensional IDCT).

[0269] In the average value synthesizing circuit 511, a regenerativesignal is derived by synthesizing the signal inversely transformed bythe inverse DCT circuit 462 with the average value 62 in the signalsinside of the content, in accordance with the resolution-transformedalpha map signal supplied from the resolution transform circuit 440.

[0270] (Fourth Preferred Embodiment)

[0271] Referring to FIGS. 41 to 44, the fourth preferred embodiment ofan image data coding and/or decoding system, according to the presentinvention will be described below.

[0272]FIG. 41 is a block diagram of an image data coding system in thisembodiment. In an average value deriving circuit 501, when the predictederror signal 30 is the edge block signal in accordance with the alphamap signal 20, the average value a of the pixels inside of the content(the portion expressed by the oblique lines in FIG. 42) is derived to besupplied to an average value inserting circuit 502. In this averagevalue inserting circuit 502, as shown in FIG. 42, the processing forassuming all the values of the pixels outside of the content to be theaverage value a of the pixels inside of the content is performed (theinsertion of the average value). By this processing, the intrablockaverage value in the square block at the center of FIG. 42 becomes a.When the signal of this intrablock average value a is supplied to theDCT circuit 230 for performing the two-dimensional DCT, the DC componentbecomes A·(=8×a) as the square block on the right-side of FIG. 42. Atthis time, an extrapolated signal may be substituted for the signaloutside of the content under the condition that the average value is a.

[0273] The output of the average value inserting circuit 502 is suppliedto the DCT circuit 230 to be transformed into a DCT coefficient, andthen, is supplied to the quantization circuit 120 to be quantizedtherein. The quantized transform coefficient is supplied to the inversequantization circuit 130 and the variable length coding circuit 140. Inthe inverse quantization circuit 130, the transform coefficient suppliedby the quantization circuit 120 is inversely transformed to be suppliedto the inverse DCT circuit.

[0274] In a pixel separating circuit 512, a regenerative picture signalis derived by separating the signals indicative of the pixels inside ofthe content from the signals inversely transformed in the inverse DCTcircuit 330, in accordance with the alpha map signal 20. At this time,the signals outside of the content are reset to be zero for example.

[0275] An image data decoding system in this embodiment will bedescribed below. FIG. 43 is a block diagram of an image data decodingsystem having the resolution transform function corresponding to theimage data coding system of FIG. 41, and FIG. 44 is a view showing amethod for reproducing a resolution-transformed signal. In FIG. 43, thetransform coefficient is inversely transformed by the inversequantization circuit 420 to be supplied to the coefficient selectingcircuit 451. In the inverse DCT circuit 462, the DCT is performed withrespect to the transform coefficient of a band required to derive adesired resolution selected by the coefficient selecting circuit 451 (inthe example of FIG. 44, a 5×5 of two-dimensional IDCT).

[0276] In a pixel separating circuit 513, a regenerative signal isderived by separating the signal inversely transformed by the inverseDCT circuit from the signals indicative of the pixels inside of thecontent, in accordance with the resolution-transformed alpha map signalsupplied from the resolution transform circuit 440.

[0277] (Fifth Preferred Embodiment)

[0278] Referring to FIGS. 45 to 49, the fifth preferred embodiment of animage data coding and/or decoding system, according to the presentinvention, will be described below.

[0279] In this embodiment, a method for coding a block of an optionalshape by the vector quantization (VQ) is used. FIG. 41 is a blockdiagram of an image data coding system in this embodiment, and FIG. 42is a view showing a method for coding in an edge block.

[0280] In FIG. 45, a vector quantizer 600 performs the matching of thepredicted error signal 30 with code vectors stored in a code book, toselect a code vector of the highest correlation to the predicted errorsignal 30. At this time, as shown in FIG. 46, with respect to the edgeblock, the matching of only the signals inside of the content (theportion expressed by the oblique lines in the drawing) with the codevectors is performed in accordance with the alpha map signal 20, tooutput an index of the code vector of the highest correlation (“2” in anexample of FIG. 46).

[0281] In the coding circuit 141, the index supplied by the vectorquantizer 600 is coded with a variable length or a fixed length to beoutputted to the multiplexer circuit 170. In an inverse vector quantizer610, as shown in FIG. 47, the signals inside of the content (the portionexpressed by the oblique lines in the drawings) are separated from thecode vector corresponding to the index supplied from the vectorquantizer 600 for outputting a regenerative signal.

[0282] An image data decoding system in this embodiment will bedescribed below.

[0283]FIG. 48 is a block diagram of an image data decoding system havingthe resolution transform function corresponding to the image data codingsystem of FIG. 45, and FIG. 49 shows code blocks provided in an inversevector quantizer 620. The alpha map signal separated by the separatingcircuit 400 from the input coding bit stream 60 is decoded by the alphamap decoding circuit 430, to be resolution-transformed into theresolution of each of picture signals by the resolution transformcircuit 440. On the other hand, the index separated by the separatingcircuit 400 is decoded by the decoding circuit 411 to be supplied to theinverse vector quantizer 620.

[0284] In the inverse vector quantizer 620, as shown in FIG. 49, a codevector of a desired resolution is selected from code vectors expressedby multiple resolution corresponding to the index, and the signal insideof the content (the portion expressed by the oblique lines in thedrawing) is separated in accordance with the resolution-transformedalpha map signal supplied from the resolution transform circuit 440. Onthe basis of this signal, a regenerative signal 70 is derived by theaddition circuit 470 and the motion compensating circuit 480.

[0285] (Sixth Preferred Embodiment)

[0286] Referring to FIGS. 50 to 53, the sixth preferred embodiment of animage data coding and/or decoding system, according to the presentinvention, will be described below.

[0287]FIGS. 50 and 52 are views explaining the subband division of apicture signal. The subband division of the input picture signal isperformed by the band division and the down sampling. FIG. 50 shows anexample that the subband division is performed by dividing the inputimage into four bands (LL, LH, HL, HH) or further dividing the band LLinto four bands to derive seven bands. FIG. 51 shows the arrangement ofeach of components on the axes of space frequencies when the subbanddivision into four bands is performed. An example of the subbanddivision of the input picture signal into four bands will be describedbelow.

[0288]FIG. 52 is a block diagram of an image data coding system in thisembodiment. The input picture signal 10 is divided into a plurality ofsubband picture signals in a subband division circuit 700, to beinputted to optional-shape coding circuits 710, 711, 712 and 713. Thesubband picture signals LL, LH, HL and HH are coded in theoptional-shape coding circuits 710, 711, 712 and 713, respectively, inan optional-shape coding method which is the same manner as thatdescribed in any one of the first to fourth preferred embodiment. Atthis time, the alpha map signals are transformed to the resolution ofeach of the subband images by a resolution transform circuit 446, to besupplied to the optional shape coding circuits 710, 711, 712 and 713,respectively. The coded alpha map signals and the subband signals areoutputted as a coding bit stream 50 through the multiplexer circuit 170.

[0289]FIG. 53 is a block diagram of an image data decoding system, inthis embodiment, adapted to the image data coding system of FIG. 52. Thealpha map signal separated by the separating circuit 400 from the inputcoding bit stream 60 is decoded by the alpha map decoding circuit 430,and the resolution transform thereof into the resolution of each of thesubband picture signals is performed by the resolution transform circuit446.

[0290] On the other hand, the subband picture signals separated by theseparating circuit 400 are inputted to the optional-shape decodingcircuits 720, 721, 722 and 723. In accordance with the alpha map signalssupplied from the resolution transform circuit 446, the subband picturesignals LL, LH, HL and HH are reproduced in the optional-shape decodingcircuits 720, 721, 722 and 723, respectively, in the same optional-shapedecoding method as that described in each of the first to fourthpreferred embodiments. That is, for example, with respect to the edgeblock, only the subband image signals inside of the content are decoded.

[0291] Each of the reproduced subband picture signals are outputted as aregenerative picture signal 70 after synthesizing only the subbandsignals necessary to derive a predetermined resolution in a subbandsynthesizing circuit 730. For example, if only the subband image LL isoutputted as the reproduced picture signal 70, the image of a lowresolution is reproduced.

[0292] Referring to FIG. 54, as an applied embodiment of the presentinvention, the preferred embodiment of an image transmitting system towhich an image data coding and/or decoding system of the presentinvention is applied, will be described below.

[0293] The picture signal inputted by a camera 1002 mounted on apersonal computer (PC) 1001 is coded by an image data coding systeminstalled in the PC 1001. The coding data outputted from this image datacoding system is multiplexed with the information on other voice anddata, to be sent by a wireless installation 1003 and received by anotherwireless installation 1004. The signal received by the wirelessinstallation 1004 is analyzed into the coding data of the picturesignals, and the information on voice and data. Among them, the codingdata of the picture signals are decoded by an image data decoding systeminstalled in a work station (EWS) 1005, to be indicated on a display ofthe EWS 1005.

[0294] On the other hand, the picture signals inputted by a camera 1006mounted on the EWS 1005 is coded using an image data coding systeminstalled in the EWS, in the same manner as that of the aforementionedmanner. The coding data are multiplexed with the other information onvoice and data, to be sent by the wireless installation 1004 andreceived by the wireless installation 1003. The signals received by thewireless installation 1003 are analyzed into the coding data of thepicture signals, and the information on voice and data. Among them, thecoding data of the picture signals are decoded by an image data decodingsystem installed in the PC 1001 to be indicated on a display of the PC1001.

[0295] Furthermore, the sending and receiving of data can be performedusing a wire transmitting system, not wireless transmitting system.

[0296] As mentioned above, according to the present invention, it ispossible to perform the resolution transform of an edge block containinga content of an optional shape, and it is also possible to code the edgeblock without reducing the coding efficiency compared with conventionalcoding methods.

What is claimed is:
 1. An image data coding system comprising:screen-area determining means for determining the area of the screenreproduced on the basis of an input image data signal; code-amountassigning control means for controlling regions to which data on thescreen are to be assigned and the code amount assigned to each of theregions, on the basis of the results determined on the area of thereproduced screen; coding means for coding said image data signalinputted in accordance with the code amount assigned to each of saidregions.
 2. An image data coding system according to claim 1, whereinsaid screen-area determining means comprises a resolution detectingcircuit for determining the area of the screen by detecting the numberof the pixels on the screen reproduced by the input image data signal,and wherein said code-amount assigning control means comprises acode-amount assigning control circuit which maintains the code amount onthe whole reproduced screen to be constant while varying a weightdistribution function for assigning the code amount to each of theregions on the screen in accordance with the number of the pixels forevery region on the reproduced screen.
 3. An image data coding systemaccording to claim 1, wherein said screen-area determining meanscomprises screen-size setting means for setting the whole area of thereproduced screen on the basis of a predetermined and known informationon the area of the screen.
 4. An image data coding system comprising:first coding means for coding a map signal indicative of the positionand shape of a content in a screen inputted for every block of picturesignals to be coded; orthogonal transform means for performing theorthogonal transform of said picture signals in accordance with said mapsignal to output an orthogonal transform coefficient; and second codingmeans for coding said orthogonal transform coefficient derived by saidorthogonal transform means, wherein said orthogonal transform meansperforms the two-dimensional orthogonal transform of the picture signalsof all the pixels with respect to the blocks located inside of thecontent, and performs the orthogonal transform of only the signals ofthe pixels contained in the content with respect to the blockscontaining the boundary portion of the content.
 5. An image datadecoding system comprising: first decoding means for decoding a codedmap signal indicative of the position and shape of a content in a screeninputted for every block of picture signals; resolution transform meansfor performing the resolution transform of the map signal decoded bysaid first decoding means; second decoding means for decoding codedorthogonal transform coefficients; coefficient selecting means forselecting an orthogonal transform coefficient necessary to reproduce animage of a predetermined resolution, from the orthogonal transformcoefficients decoded by said second decoding means, on the basis of themap signal resolution-transformed by said resolution transform means;inverse orthogonal transform means for performing the inverse orthogonaltransform of the orthogonal transform coefficient selected by saidcoefficient selecting means and reproducing means for deriving aregenerative picture signal resolution-transformed from the results ofthe inverse orthogonal transform by said inverse orthogonal transformmeans, wherein said inverse orthogonal transform means performs thetwo-dimensional orthogonal transform of all the coefficients withrespect to the blocks located inside of the content among the orthogonaltransform coefficients selected by said coefficient selecting means, andperforms the inverse orthogonal transform of only the coefficientscontained in the content with respect to the blocks containing theboundary portion of the content.
 6. An image data coding systemcomprising: first coding means for coding a map signal indicative of theposition and shape of a content in a screen inputted for every squareblock of picture signals to be coded; average value separating means foroutputting the values of pixels, in the manner of outputting an averagevalue of pixels when blocks include a boundary of the content,outputting a difference value between the average value and a pixelvalue when blocks are inside of the content, and outputting a zero valuewhen blocks are outside of the content; orthogonal transform means forperforming the two-dimensional orthogonal transform of the signals fromwhich the average value has been separated by said average valueseparating means, to output orthogonal transform coefficients; andsecond coding means for coding said orthogonal transform coefficientsoutputted by said orthogonal transform means, and said average value. 7.An image data decoding system comprising: first decoding means fordecoding a coded map signal indicative of the position and shape of acontent in a screen inputted for every block of picture signals;resolution transform means for performing the resolution transform ofthe map signal decoded by said first decoding means; second decodingmeans for decoding coded orthogonal transform coefficients and anaverage value of pixels inside of said content; coefficient selectingmeans for selecting an orthogonal transform coefficient necessary toreproduce an image of a predetermined resolution, from the orthogonaltransform coefficients decoded by said second decoding means, on thebasis of the map signal resolution-transformed by said resolutiontransform means; inverse orthogonal transform means for performing thetwo-dimensional inverse orthogonal transform of the orthogonal transformcoefficient selected by said coefficient selecting means; andreproducing means for deriving a resolution-transformed regenerativepicture signal by synthesizing the results of the two-dimensionalinverse orthogonal transform by said inverse orthogonal transform means,with said average value decoded by said second decoding means, on thebasis of said map signal resolution-transformed by said resolutiontransform means.
 8. An image data coding system comprising: first codingmeans for coding a map signal indicative of the position and shape of acontent in a screen inputted for every square block of picture signalsto be coded; average value inserting means for replacing the values ofpixels outside of the content by an average value of the values ofpixels inside of the content in accordance with said map signal, withrespect to the blocks containing the boundary portion of the content insaid picture signals; orthogonal transform means for performing thetwo-dimensional orthogonal transform of the signal of the average valuein the blocks produced by said average value inserting means, to outputorthogonal transform coefficients; and second coding means for codingsaid orthogonal transform coefficients outputted by said orthogonaltransform means.
 9. An image data decoding system comprising: firstdecoding means for decoding a coded map signal indicative of theposition and shape of a content in a screen inputted for every squareblock of picture signals; resolution transform means for performing theresolution transform of the map signal decoded by said first decodingmeans; second decoding means for decoding coded orthogonal transformcoefficients; coefficient selecting means for selecting an orthogonaltransform coefficient necessary to reproduce an image of a predeterminedresolution, from the orthogonal transform coefficients decoded by saidsecond decoding means, on the basis of the map signalresolution-transformed by said resolution transform means; inverseorthogonal transform means for performing the two-dimensional inverseorthogonal transform of the orthogonal transform coefficient selected bysaid coefficient selecting means; and reproducing means for deriving aresolution-transformed regenerative picture signal by taking out thevalues of pixels inside of the content from the results of thetwo-dimensional inverse orthogonal transform by said inverse orthogonaltransform means, with respect to the blocks containing the boundaryportion of the content, on the basis of the map signalresolution-transformed by said resolution transform means.
 10. An imagedata coding system comprising: first coding means for coding a mapsignal indicative of the position and shape of a content in a screeninputted for every square block of picture signals to be coded; vectorquantizing means for quantizing said picture signals in the manner ofmatching said picture signal with code vectors stored in a code book 80as to output an index indicative of a code vector which has the highestcorrelation to said picture signal when blocks are inside of thecontent, and matching only the signals inside of the content with saidcode vectors when blocks contain the boundary portion of the content inaccordance with said map signal; and second coding means for coding saidindex outputted by said vector quantizing means.
 11. An image datadecoding system comprising: first decoding means for decoding a codedmap signal indicative of the position and shape of a content in a screeninputted for every block of picture signals to be coded; resolutiontransform means for performing the resolution transform of the mapsignal decoded by said first decoding means; second decoding means fordecoding a coded index; and inverse vector quantizing means, having acode book storing therein code vectors indicated by multipleresolutions, for outputting a code vector of a desired resolutiondesignated by the index decoded by said second decoding means whenblocks are inside of the content, and deriving a resolution-transformedregenerative picture signal by taking out only the signal inside of thecontent when the blocks contain the boundary portion of the content,from the code vectors according to the map signal resolution-transformedby said resolution transform means.
 12. An image data coding systemcomprising: first coding means for coding a map signal indicative of theposition and shape of a content in a screen inputted for every squareblock of picture signals to be coded; subband dividing means fordividing said picture signal into a plurality of subband picturesignals; resolution transform means for performing the resolutiontransform of said map signal into the resolution of each of the subbandpicture signals divided by said subband dividing means; and secondcoding means for coding each of the subband picture signals divided bysaid subband dividing means when blocks are inside of the content, andcoding only the signals inside of the content when the blocks containthe boundary portion of the content in said subband picture signalsaccording to the map signal resolution-transformed by said resolutiontransform means.
 13. An image data decoding system comprising: firstdecoding means for decoding a coded map signal indicative of theposition and shape of a content in a screen inputted for every squareblock of picture signals to be coded; resolution transform means forperforming the resolution transform of the map signal decoded by saidfirst decoding means, into the resolutions of a plurality of subbandpicture signals; second decoding means for decoding a plurality of codedsubband signals; and subband synthesizing means for deriving aresolution-transformed regenerative picture signal by synthesizing onlythe subband picture signals necessary to reproduce an image of apredetermined resolution among the plurality of subband picture signalsdecoded by said second decoding means, wherein said second decodingmeans decodes only the subband picture signals inside of the contentwith respect to the blocks containing the boundary portion of thecontent among the subband picture signals, in accordance with the mapsignal resolution-transformed by said resolution transform means.